1. Field of the Invention
The apparatus and method of the present invention relates to securing of flanges onto a pipeline, and more particularly relates to an apparatus and process for assuring that flanges welding to a pipeline due to a break in the pipeline may be secured without leaks and create a safety zone for workers undertaking the welding process.
2. General Background
In pipelines for transporting gas under pressure at great distances, often times a section of the pipeline must be replaced due to a break in the pipeline or other problems confronted. Therefore, the source of the pressurized gas must be shut down, and a section of the pipeline must be replaced. Of course, in replacement, the pipeline must be cut and a new section welded thereupon.
The major problem confronted in this situation, is the existing volume of gas which is retained in the pipeline even after the source of gas has been shut down. Therefore, it is imperative that the volume of gas either be removed from the pipeline, or that a safety zone be created for the welders who must place the section of pipe in the line. The most difficult problem is the removal of the gas from the line, which has been attempted in various methods. One such method may be to attempt to vent the gas from the pipeline, by the use of a "pig" pushed through the line from its source so that it would push the volume of gas from the line. This process is an extremely expensive and time consuming process and has been found to be prohibitively expensive. An additional method is to pump a plug of nitrogen into the open end of the pipeline and literally push the volume of gas away from the end of the line so that the welders may work within this gas free zone. One of the problems in this particular area is the fact that if the nitrogen plug would back out of the line into the areas where the workers are working, the nitrogen would in effect replace any oxygen in the area and the welders would suffocate due to the lack of oxygen. Of course, the most obvious problem in this area, is the fact that if no precautions are taken to care for the safety of the welders, then any spark or the like would result in a catastrophic explosion and fire of the gas within the pipeline.